Template‐Assisted Formation of High‐Quality α‐Phase HC(NH₂)₂PbI₃ Perovskite Solar Cells

Abstract

Formamidinium (FA) lead halide (α‐FAPbI3) perovskites are promising materials for photovoltaic applications because of their excellent light harvesting capability (absorption edge 840 nm) and long carrier diffusion length. However, it is extremely difficult to prepare a pure α‐FAPbI3 phase because of its easy transformation into a nondesirable δ‐FAPbI3 phase. In the present study, a “perovskite” template (MAPbI3‐FAI‐PbI2‐DMSO) structure is used to avoid and suppress the formation of δ‐FAPbI3 phases. The perovskite structure is formed via postdeposition involving the treatment of colloidal MAI‐PbI2‐DMSO film with FAI before annealing. In situ X‐ray diffraction in vacuum shows no detectable δ‐FAPbI3 phase during the whole synthesis process when the sample is annealed from 100 to 180 °C. This method is found to reduce defects at grain boundaries and enhance the film quality as determined by means of photoluminescence mapping and Kelvin probe force microscopy. The perovskite solar cells (PSCs) fabricated by this method demonstrate a much‐enhanced short‐circuit current density ( J sc) of 24.99 mA cm−2 and a power conversion efficiency (PCE) of 21.24%, which is the highest efficiency reported for pure FAPbI3, with great stability under 800 h of thermal ageing and 500 h of light soaking in nitrogen.

Enhanced Performance of Planar Perovskite Solar Cells Induced by Van Der Waals Epitaxial Growth of Mixed Perovskite Films on WS2 Flakes

“…[ 43 ] The trap density can be calculated by trap‐filled limit voltage ( V TFL ) with the equation of n t = (2 εε 0 V TFL )/( qL 2 ), where ε is the dielectric constants of perovskite, ε 0 is the vacuum permittivity, and q is the elite layer. [ 44 ] V TFL could be obtained by fitting the I – V curves. The defect densities of the perovskite films are estimated to be 1.94 × 10 15 and 0.68 × 10 15 cm −3 for the devices without and with the WS 2 interlayer, respectively.…”

Halide Perovskite Materials for Energy Storage Applications

“…The cubic→tetragonal→orthorhombic phase transitions of the CH 3 NH 3 PbI 3 (MAPbI 3 ) occur at 330 and 160 K. [29] A nonperovskite δ phase is also available in some halide perovskites such as HC(NH 2 ) 2 PbI 3 , HC(NH 2 ) 2 PbI 3 (FAPbI 3 ), CsPbI 3 , and CsSnI 3 . [29][30][31] Compositional engineering the chemical species in halide perovskites are effective to tune the structures and optoelectronic properties (Figure 1b). [8] The incorporation of inorganic species such Cs often leads to improved stability.…”

“…The cubic→tetragonal→orthorhombic phase transitions of the CH 3 NH 3 PbI 3 (MAPbI 3 ) occur at 330 and 160 K. [ 29 ] A nonperovskite δ phase is also available in some halide perovskites such as HC(NH 2 ) 2 PbI 3 , HC(NH 2 ) 2 PbI 3 (FAPbI 3 ), CsPbI 3 , and CsSnI 3 . [ 29–31 ]…”

Advanced partial nucleation for single-phase FA0.92MA0.08PbI3-based high-efficiency perovskite solar cells

“…6b). This was because the MCP method is beneficial for an even morphology and uniform dense layer [41,42].…”